The broad objective of this proposal is to examine the mechanisms by which the noradrenergic neurones of the inferior mesenteric ganglion and celiac ganglion regulate intrinsic neural control mechanisms in the gastrointestinal tract of the guinea pig, rat and rabbit. The major emphasis will be on ganglia in the guinea pig. The areas of particular interest are (a) the nature and location of the "driver" neurone, (b) control of activity in parasympathetic, pelvic nerves and intrinsic cholinergic neurones by sympathetic ganglion cells in the inferior mesenteric ganglion, (c) control of smooth muscle excitability by the inferior mesenteric ganglion and (d) the occurrence of reflex activity between the celiac ganglion and the stomach and upper small bowel. The general method of approach will be the measurement of electrical activity of single ganglion cells in vitro with the intracellular recording technique. BIBLIOGRAPHIC REFERENCES: Weems, W.A. and J.H. Szurszewski: Responses of neurons in the inferior mesenteric ganglion to repetitive stimulation of preganglionic inputs. Fed. Proc. 34:423, 1975. Weems, W.A. and J.H. Szurszewski: Relative capabilities of different preganglionic inputs to the IMG to control colonic motility. Physiologist. 18:439, 1975.